// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
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// modification, are permitted provided that the following conditions
// are met:
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//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
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//    this software without specific prior written permission.
//
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package cn.taketoday.context.asm;

/**
 * A visitor to visit a Java annotation. The methods of this class must be
 * called in the following order: ( {@code visit} | {@code visitEnum} |
 * {@code visitAnnotation} | {@code visitArray} )* {@code visitEnd}.
 *
 * @author Eric Bruneton
 * @author Eugene Kuleshov
 */
public abstract class AnnotationVisitor {

  /**
   * The annotation visitor to which this visitor must delegate method calls. May
   * be null.
   */
  protected AnnotationVisitor av;

  /**
   * Constructs a new {@link AnnotationVisitor}.
   */
  public AnnotationVisitor() {
    this(null);
  }

  /**
   * Constructs a new {@link AnnotationVisitor}.
   *
   * @param annotationVisitor
   *         the annotation visitor to which this visitor must delegate method
   *         calls. May be null.
   */
  public AnnotationVisitor(final AnnotationVisitor annotationVisitor) {
    this.av = annotationVisitor;
  }

  /**
   * Visits a primitive value of the annotation.
   *
   * @param name
   *         the value name.
   * @param value
   *         the actual value, whose type must be {@link Byte},
   *         {@link Boolean}, {@link Character}, {@link Short}, {@link Integer}
   *         , {@link Long}, {@link Float}, {@link Double}, {@link String} or
   *         {@link Type} of {@link Type#OBJECT} or {@link Type#ARRAY} sort.
   *         This value can also be an array of byte, boolean, short, char,
   *         int, long, float or double values (this is equivalent to using
   *         {@link #visitArray} and visiting each array element in turn, but
   *         is more convenient).
   */
  public void visit(final String name, final Object value) {
    if (av != null) {
      av.visit(name, value);
    }
  }

  /**
   * Visits an enumeration value of the annotation.
   *
   * @param name
   *         the value name.
   * @param descriptor
   *         the class descriptor of the enumeration class.
   * @param value
   *         the actual enumeration value.
   */
  public void visitEnum(final String name, final String descriptor, final String value) {
    if (av != null) {
      av.visitEnum(name, descriptor, value);
    }
  }

  /**
   * Visits a nested annotation value of the annotation.
   *
   * @param name
   *         the value name.
   * @param descriptor
   *         the class descriptor of the nested annotation class.
   *
   * @return a visitor to visit the actual nested annotation value, or
   * {@literal null} if this visitor is not interested in visiting this
   * nested annotation. <i>The nested annotation value must be fully
   * visited before calling other methods on this annotation visitor</i>.
   */
  public AnnotationVisitor visitAnnotation(final String name, final String descriptor) {
    if (av == null) {
      return null;
    }
    return av.visitAnnotation(name, descriptor);
  }

  /**
   * Visits an array value of the annotation. Note that arrays of primitive types
   * (such as byte, boolean, short, char, int, long, float or double) can be
   * passed as value to {@link #visit visit}. This is what {@link ClassReader}
   * does.
   *
   * @param name
   *         the value name.
   *
   * @return a visitor to visit the actual array value elements, or
   * {@literal null} if this visitor is not interested in visiting these
   * values. The 'name' parameters passed to the methods of this visitor
   * are ignored. <i>All the array values must be visited before calling
   * other methods on this annotation visitor</i>.
   */
  public AnnotationVisitor visitArray(final String name) {
    if (av == null) {
      return null;
    }
    return av.visitArray(name);
  }

  /** Visits the end of the annotation. */
  public void visitEnd() {
    if (av != null) {
      av.visitEnd();
    }
  }
}
